Structural and magnetic properties of Sr0.5Co0.5Fe2O4 nanoferrite

The nanoparticle Sr0.5Co0.5Fe2O4 powder was produced via glycol-thermal process from high-purity metal chlorides at a low reaction temperature of 200 degrees C. The phase identification of the as-synthesized powder reveals cubic spine! structure with an average crystallite size of 8 nm. Room-temperature Mossbauer spectra for the as-synthesized sample and samples annealed at different temperatures show different local environments of tetrahedral and octahedral coordinated iron cations. Magnetic properties of the as-synthesized sample and samples annealed at 300, 400, 450, 500, 600, 700 and 800 degrees C have been investigated using a vibrating sample magnetometer at room-temperature in applied magnetic fields of up to about 1.4 T. A substantial increase in coercive field at 300 K from 0.28 kOe to 2.897 kOe was obtained for the as-synthesized and annealed sample at 800 C. Magnetic field dependence of magnetization curves measured on a mini-cryogen free VTI system operating at a base temperature of 2 K in magnetic fields of up to 5 T have been investigated. The variation of the saturation magnetization as a function of temperature follows modified Bloch's law. Coercive field increased from about 0.28 kOe and 1.04 kOe at 300 K to 11.14 kOe and 10.43 kOe at 2 K for the as-synthesized sample and sample annealed at 500 degrees C, respectively because of spin-freezing. The effect of exchange bias and Kneller's law are used to account for the temperature dependence of coercive fields. (C) 2014 Elsevier B.V. All rights reserved.